Min left home at 11.45 a.m. and drove towards the countryside. 2 hours later, her older brother left their home and drove towards the same countryside at 100 km/h. When the older brother reached the countryside at 4.45 p.m., Min had another 4 km to travel. What was Min’s average speed? Express your answer in mixed number.
Time that the Min's older brother started driving = 1.45 p.m.
Duration that Min's older brother drove from 1.45 p.m. to 4.45 p.m. = 3 h

Distance that Min's older brother travelled
= 3 x 100
= 300 km

Distance that Min travelled by the time her older brother reached the city
= 300 - 4
= 296 km

Time that Min took to travel 296 km = 5 h

Min's average speed
= 296 ÷ 5
= 59¹₅ km/h

Answer(s): 59¹₅ km/h